Chamber shrink wrapping machine

ABSTRACT

A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the body defines longitudinal and transverse horizontal air ducts in the lower portion of the chamber to direct heated air toward the L-sealer and around the product.

FIELD OF THE INVENTION

The present invention relates to chamber shrink wrapping machines.

BACKGROUND OF THE INVENTION

Semi-automatic, hand-fed chamber shrink wrapping machines are capable of sealing and shrinking heat-shrinkable film in a single operation. Such machines have a chamber defined by a machine body and a hinged hood having an integral L-sealer. A product to be wrapped is placed by an operator into longitudinally centre-folded heat-shrinkable film on a product tray. The product in the film is then manually moved into the chamber where it is statically supported on an exit conveyor adjacent the L-sealer. The hood is then automatically lowered by a servo-mechanism to activate the L-sealer to seal and cut the film around the product, and heated air is supplied to the chamber to shrink the film onto the product. After a predetermined shrinking time, the hood is automatically raised, and the exit conveyor conveys the shrink-wrapped product out of the chamber for the wrapping cycle to start again.

Conventionally PVC film has been used in shrink wrap machines, though Polyolefin film has recently been used. Polyolefin film requires higher temperatures to effectively shrink wrap a product, thus increasing the importance of optimising a shrink wrap machine to efficiently use heat. The ability of a shrink wrap machine to generate, distribute and retain heat efficiently is an important performance characteristic that can influence energy use and process cycle times.

One disadvantage of conventional chamber shrink wrapping machines is that an L-shaped gap must be left between the edge of the product and the bars of L-sealer to ensure that heated air can flow around and over the product. Typically, the gap varies from 20 to 80 mm depending on the size and height of the product to be wrapped. The gap increases heated air flow, but also increases the amount of film used, which in turn increases the shrinking time and decreases energy efficiency.

Another disadvantage is that the automatic lowering and raising of the hood can allow an undesirable amount of heat to escape if an operator is not attentive to the machine. For automatic operation of the hood to provide sufficient force to positively seal the chamber and prevent excessive heat loss creates a safety risk to operators whose hands can be caught between the machine body and the hood during closing of the chamber. Electronic cut-out switches have been proposed to stop the hood lowering after a predetermined time when the hood encounters an obstacle. Such electronic safety switches are complicated and expensive and are thought to be less reliable than a mechanical failsafe.

What is needed is a chamber shrink wrapping machine which addresses the above difficulties.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the body defines longitudinal and transverse horizontal air ducts in the lower portion of the chamber to direct heated air toward the L-sealer and around the product.

The ducts can peripherally surround the roller conveyor to allow heated air to flow therearound. The ducts can be formed as horizontal elongate slots. According to the present invention, there is also provided a chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the roller conveyor has a plurality of parallel rollers that are transversely skewable and rotatable to subsequently convey the product longitudinally and transversely away from the L-sealer towards the centre of the chamber to allow heated air to circulate around the product to shrink the film thereon, and wherein the plurality of rollers are transversely unskewable and rotatable to finally convey the shrink-wrapped product longitudinally out of the chamber when the hood is raised.

The plurality of rollers can be rotatably and transversely skewably supported between two parallel side rails, one of which is fixed to the body and the other of which is longitudinally movable relative thereto to thereby collectively transversely skew the plurality of rollers.

One end of each roller can be rotatably and transversely skewably mounted to the fixed side rail by a spring, and the other end of each roller can be rotatably and longitudinally slidably mounted in an elliptical seat in the movable side rail.

According to the present invention, there is further provided a chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, and a hood actuator, wherein the hood actuator is arranged to support the weight of the hood whilst it is lowered and then clamp the hood in a closed position.

The hood actuator can include a strut to support the hood, the strut being coupled to a spring loaded over-centre lever arranged to resist movement of the strut, and thereby support the weight of the hood, as the hood is lowered and then draw the strut downwards to clamp the hood closed. The over-centre lever can be loaded by a tension spring fixed to the body of the machine.

The hood actuator can be driven to lower the hood, the hood actuator having a one-way clutch that allows the hood to be idly raised.

The machine can further include a drive gear fixed to a motor, a free gear fixed to the one way clutch and an engagement device to rotationally fix the fixed gear to the free gear to transmit drive from the motor to lower the hood. The engagement device can be a gear which can be brought into contact with fixed gear and the free gear. The engagement gear can be arranged to be brought into engagement by moving the hood from an initial upright position to a closed position.

The hood actuator can be driven by a reduction drive electric motor. The motor can be pivotably mounted on a sprung base so that the motor moves against the action of the springs when the hood is closed to clamp the hood in a closed position.

The machine can further include a controller to control the hood actuator and can include a controller to control the air heater and the roller conveyor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described by way of example only with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an embodiment of a chamber shrink wrapping machine of the invention;

FIG. 2 is a section through the machine;

FIG. 3 is a perspective view of the chamber of the machine;

FIG. 4 is a plan view of the skewable roller conveyor of the machine;

FIG. 5 is plan view of rollers in an unskewed and skewed position;

FIG. 6 is a perspective view of a manual hood actuator of the machine;

FIG. 7 is a side view of the manual hood actuator fitted to the machine;

FIGS. 8 and 9 are side views of the manual hood actuator in respective first and second conditions corresponding to the hood being open and closed respectively;

FIG. 10 is a perspective view of a semi-automatic hood actuator of the machine;

FIG. 11 is a side view of the semi-automatic hood actuator fitted to the machine;

FIGS. 12 and 13 are end views of the semi-automatic hood actuator in respective first and second conditions corresponding to the hood being open and closed respectively; and

FIG. 14 is a side view of the semi-automatic hood actuator in a condition corresponding to the hood being clamped.

DETAILED DESCRIPTION

FIG. 1 illustrates an embodiment of a chamber shrink wrapping machine 10 of the invention. The machine 10 has a longitudinal body 12 defining a lower portion of a chamber 14, and a hood 16 with an integral L-sealer 18 transversely hinged to the body 12 to define an upper portion of the chamber 14 when lowered. The hood 16 is formed, for example, as a transparent housing mounted to a frame, wherein the L-sealer is integrated in adjacent, mutually orthogonal sides of the frame. A height-adjustable, horizontal roller conveyor 20 is mounted to the body 12 in the lower portion of the chamber 14. Roll holders 22 are mounted to one end of the body 12 to rotatably hold rolls 24 of longitudinal centre-folded heat-shrinkable film (not shown). A controller 26 and a product tray 28 are mounted to the body 12 between the chamber 14 and the roll holders 22.

Referring to FIG. 2, an air heater 30, comprising a heating element 32 and an upwardly directed fan 34, is mounted in the body 12 under the chamber 14 to supply heated air into the chamber 14 to heat shrink film onto a product (not shown) to be wrapped. To withstand the high temperatures required for shrinking Polyolefin without suffering deformation, the blades of fan 34 are made of a material capable of withstanding high temperatures, such as steel for example. Due to the increased weight of steel, holes may be formed in the fan 34 to reduce its weight and moment of inertia.

The body 12 of the machine 10 defines longitudinal and transverse horizontal air ducts 13 in the lower portion of the chamber below the sealing bar in mutually orthogonal sides of the body 12 to peripherally surround sides of the roller conveyor 20 adjacent where the L-sealer 18 contacts the body 12 to allow heated air to flow around a product (not shown) to be wrapped. For example, the chamber 14 is defined by longitudinal and transverse vertical panels 15 a, 15 b, as shown in FIG. 1, and the air ducts are partially defined by channels formed in the panels 15 a, 15 b and open into horizontal elongate slots between an upper portion of the panels 15 and the rollers 42.

A hood actuator 35 is mounted in the body 12 to guide movement of the hood 16. In the example shown, the hood actuator 35 includes a strut 36 driven by a motor 38 via a one-way clutch 40 to automatically reciprocally lower and raise the hood 16. In one example, the hood actuator 35 is arranged to allow the hood 16 to be drivingly raised but idly lowered under its own weight so that an operator's hands can be easily withdrawn if caught under the hood 16 during closing of the chamber 14. The hood actuator 35, the roller conveyor 20, and the air heater 30 are controlled by the controller 26 which is programmed with different operating programs for products of different sizes and heights.

Referring to FIGS. 3 to 5, the roller conveyor 20 has a plurality of spaced, parallel rollers 42 rotatably and transversely skewably supported between two parallel side rails 44, 46. One of the side rails 44 is fixed, while the other side rail 46 is longitudinally movable relative to the fixed side rail 44 to thereby collectively transversely skew the rollers 42. The movable side rail 46 is longitudinally movable by a servo-mechanism (not shown) controlled by the controller 26. The rollers 42 are rotatable by a motor 48 having a motor sprocket 50 connected to roller sprockets 52 by a chain (not shown). The motor 48 is also controlled by the controller 26. One end of each roller 42 is rotatably and transversely skewably mounted to the fixed side rail 44 by a spring 48 mounted on a sprocket shaft 54 of the roller sprocket 52, and the other end of each roller 42 is rotatably and longitudinally slidably mounted in an elliptical seat 58 in the movable side rail 46. Other equivalent rotatable and transversely skewable mounting arrangements, for example articulated universal or cardan joints, may also be used for the rollers 42. FIG. 4 illustrates the rollers 42 in a transversely unskewed position so that their axes of rotation are collectively generally orthogonal to the side rails 44, 46. FIG. 5 illustrates the transverse skewing of a roller 42 so its axis of rotation is generally inclined at an acute angle to the side rails 44, 46.

In use, the rollers 42 are initially oriented in an unskewed position to statically support a product (not shown) to be wrapped in the chamber 14 longitudinally and transversely closely adjacent the L-sealer 18 during sealing and cutting of heat-shrinkable film around the product when the hood 16 is lowered. The rollers 42 are subsequently automatically transversely skewed and rotated to convey the product longitudinally and transversely away from the L-sealer 18 towards the centre of the chamber 14 to allow heated air to circulate around the product to shrink the film thereon. Finally, the rollers 42 are transversely unskewed and rotated to convey the shrink-wrapped product longitudinally out of the chamber 14 when the hood 16 is raised.

FIGS. 6 to 9 illustrate a manual hood actuator 60 for supporting the weight of the hood 16 whilst it is lowered to prevent accidental slamming on the hood. The hood actuator 60 also clamps the hood in the closed position once lowered so that the chamber 14 can be positively closed and pressurised. The weight of the hood 16 is balanced by spring 68 so that only a small amount of force is required to open or close the hood.

As illustrated in FIG. 7, the hood actuator 60 is coupled to the hood 16 by a strut 36. The strut 36 is coupled, via crank arm 62 and shaft 64, to a spring loaded lever 66 which is arranged for over-centre operation. In this regard, the spring 68 acts upon the lever 66 to resist rotation during an initial portion of its travel. Once the spring passes over a pivot point of the lever 66, the tension in the spring urges the lever onward. In the illustrated hood actuator 60, this acts to support the weight of the hood whilst it is lowered and then clamps the hood closed.

FIGS. 7 and 8 illustrate the hood 16 in an open position. The strut 36 is fixed to the hood 16 and the hood actuator 60 by adjustable tie rod ends 37 a, 37 b respectively, which allow fine tuning of the hood actuator 60. As illustrated in FIG. 8, the tension spring 68 acts upon lever 66 to resist movement of the strut 36, thereby supporting the weight of the hood 16. As the hood is closed, the strut 36 will move downwards and cause the lever 66 to rotate counter-clockwise and stretch the spring. As illustrated in FIG. 9, once the spring passes over pivot point 67 of the lever 66, the tension in the spring 68 will urge the lever 66 further counter-clockwise, thereby urging the strut 36 downwards to clamp the hood 16 in a closed position.

The spring 68 is fixed to the machine 10 by an elongate washer 65 and a screw 69. The screw 69 can be received by the machine 10 in different locations so as to be vertically adjustable to change the point at which the weight of the hood is no longer supported and the hood becomes clamped, thereby providing fine tuning of the closing operation of the hood. The elongate washer 65 is provided to allow the tension of the spring 68 to be adjusted to increase the clamping force on the closed hood or to accommodate for hoods of different weight.

As illustrated in FIG. 8, a screw 71 is provided to allow adjustment of the angle between levers 62 and 66. Screws 73 and 75 are also arranged to be brought into contact with each other to prevent over-extension of the strut.

FIGS. 10 to 14 illustrate a semi-automatic hood actuator 70 for lowering the hood 16. The hood actuator 70 has a motor 72 and a drive plate 74 coupled to the motor 70 by a one-way clutch to close the hood 16 and allow it to be idly raised. The motor 72 drives a first gear 76 fixed thereto and disposed adjacent to a second gear 78 which is driven by the one-way clutch to draw the hood 16 downward. An engagement gear 80 is mounted to a spring loaded lever 82 and disposed above the first gear 76 and the second gear 78.

FIGS. 11 and 12 illustrate the hood 16 in an open position with the strut 36 in a higher vertical position. The strut 36 is fixed to the hood 16 and the hood actuator 70 by adjustable tie rod ends 37 a, 37 b. Spring 68 is in an un-stretched condition to support the weight of the hood 16.

As illustrated in FIG. 12, the collar 84 is mounted to the strut 36 by a compression spring 90 so that the force between the engagement gear 80 and the first and second gears 76, 78 does not cause the first and second gears 76, 78 to lock. An adjustable collar 91 is provided so that the compression of the spring 90 can be adjusted. An adjustable collar 93 is provided to adjust the point at which the engagement gear engages the first and second gears 76,78.

The strut 36 is drawn downward by the action of the motor 72 but can be stopped at any point prior to being closed as the one-way clutch allows the drive disc 74 to be rotated against the action of the motor 72.

As illustrated in FIG. 13, as the strut 36 is drawn downward and the hood is closed, the collar 84 is brought into contact with the spring loaded lever 82 to urge the engagement gear 80 downward and into engagement with the first gear 76 and the second gear 78 to lock them together, thus transferring direct drive power from the motor 72 to drive disc 74, bypassing the one-way clutch, and causing drive disc 74 to rotate to draw the strut 36 further downwards to positively drive the hood 16 closed so that the chamber is sealed and heating air retained in the chamber.

As illustrated in FIG. 14, the motor 72 is fixed to a plate 81 which is pivotally mounted on a bearing 86 and supported by springs 88 so that when the engagement gear 80 locks the first and second gears 76, 78, the motor 72 pivots against the force of the springs to clamp the hood 16 closed and positively seal the chamber 14 and retain heating air. Once the motor 72 has pivoted a pre-determined amount, a limit switch will be activated to stop the motor 72.

After a predetermined amount of time has elapsed for the film to be shrunk, for example 0.7 to 1.0 sec, the motor 72 will reverse to open the hood 16. Once the spring loaded lever 82 moves a sufficient distance, the engagement gear 80 disengages from the first and second gears 76 and 78 to free the drive plate 74 so that it can rotate, via the one-way clutch, to allow the strut 36 to be lifted, thus releasing the hood 16.

It will be appreciated that the semi-automatic hood actuator 70 incorporates a number of components describe in relation to hood actuator 60, as shown in FIGS. 6 to 9, to assist the operation of the drive unit so that a less powerful motor can be used. In this regard, it can be seen in FIG. 14 that spring 68 acts to assist the hood actuator 70.

It will be appreciated that embodiments of the invention provide a semi-automatic, hand-fed chamber shrink wrapping machine capable of automatically positioning a product centrally in a shrink wrap chamber after sealing and cutting of shrink film by an L-sealer.

The diverging exit roller conveyor of embodiments of the invention reduces shrink film consumption, as well as shrink time and energy consumption. In addition, the hood actuator of embodiments of the invention provides a simple mechanical solution which improves operator safety during automatic hood raising and lowering and may be suitable for use in other applications.

The embodiments have been described by way of example only and modifications are possible within the scope of the claims which follow. 

1. A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the body defines longitudinal and transverse horizontal air ducts in the lower portion of the chamber to direct heated air toward the L-sealer and around the product.
 2. A machine according to claim 1, wherein the ducts peripherally surround the roller conveyor to allow heated air to flow therearound.
 3. A machine according to claim 1, wherein the ducts are formed as horizontal elongate slots.
 4. A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the roller conveyor has a plurality of parallel rollers that are transversely skewable and rotatable to subsequently convey the product longitudinally and transversely away from the L-sealer towards the centre of the chamber to allow heated air to circulate around the product to shrink the film thereon, and wherein the plurality of rollers are transversely unskewable and rotatable to finally convey the shrink-wrapped product longitudinally out of the chamber when the hood is raised.
 5. A machine according to claim 4, wherein the plurality of rollers are rotatably and transversely skewably supported between two parallel side rails, one of which is fixed to the body and the other of which is longitudinally movable relative thereto to thereby collectively transversely skew the plurality of rollers.
 6. A machine according to claim 5, wherein one end of each roller is rotatably and transversely skewably mounted to the fixed side rail by a spring, and the other end of each roller is rotatably and longitudinally slidably mounted in an elliptical seat in the movable side rail.
 7. A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, and a hood actuator, wherein the hood actuator is arranged to support the weight of the hood whilst it is lowered and then clamp the hood in a closed position.
 8. A machine according to claim 7, wherein the hood actuator includes a strut to support the hood, the strut being coupled to a spring loaded over-centre lever arranged to resist movement of the strut, and thereby support the weight of the hood, as the hood is lowered and then draw the strut downwards to clamp the hood closed.
 9. A machine according to claim 8, wherein the over-centre lever is loaded by a tension spring fixed to the body of the machine.
 10. A machine according to claim 7, wherein the hood actuator is driven to lower the hood, the hood actuator having a one-way clutch that allows the hood to be idly raised.
 11. A machine according to claim 10, further including a drive gear fixed to a motor, a free gear fixed to the one way clutch and an engagement device to rotationally fix the fixed gear to the free gear to transmit drive from the motor to lower the hood.
 12. A machine according to claim 11, wherein the engagement device is a gear which can be brought into contact with fixed gear and the free gear.
 13. A machine according to claim 12, wherein the engagement gear is arranged to be brought into engagement by moving the hood from an initial upright position to a closed position.
 14. A machine according to claim 10, wherein the hood actuator is driven by a reduction drive electric motor.
 15. A machine according to claim 14, wherein the motor is pivotably mounted on a sprung base so that the motor moves against the action of the springs when the hood is closed to clamp the hood in a closed position.
 16. A machine according to claim 10, further including a controller to control the hood actuator.
 17. A machine according to claim 1, further including a controller to control the air heater and the roller conveyor. 